1. Field of the Invention
The present invention relates to analyzing coatings on electrically conducting materials, and in particular, analyzing non-conducting coatings on electrically conducting substrates.
2. Problems in the Art
Many metal parts utilized in critical situations have coatings which attempt to protect those part from high temperature, chemicals, wear, or other dangers. An example is coatings on the metal parts of jet aircraft engines; these coatings are called thermal barrier coatings (TBC) and play a critical role in current airplane technology.
Coatings are also utilized to provide barriers to chemical attack, to improve wear, and to provide other desirable mechanical properties.
As can be appreciated, many coatings are relatively thin and therefore, to be effective, it is essential that their thickness and integrity be as uniform and complete as possible. For example, thermal barrier coatings are typically 100 to 500 micrometer thick layers of ceramic materials such as yttria-stabilized zirconia bonded to a metallic component. Obviously, thermal barrier coatings have low thermal conductivity which limits the heat load to the metal part in a high temperature environment.
Many coatings of these types are bonded directly to the metal substrate. Once bonded, there is no easy way to evaluate the coating for thickness and integrity.
Attempts have been made to nondestructively evaluate coatings, but to present, these attempts have not adequately been able to characterize relevant defects such as inadequate thickness, porosity, disbonds or cracks at the coating/substrate interface, or other flaws. A real need therefore exists for a nondestructive evaluation (NDE) technique which can measure the protection offered by the coating, for example, its thermal resistance, and/or determine the coating's structural integrity.
It is therefore a principal object of the present invention to provide a means and method for nondestructively analyzing coatings on electrically conducting materials which solves or improves over the problems and deficiencies in the art.
A further object is to present a means and method as above described which is nondestructive and accurate in measuring characteristics such as inadequate thickness, porosity, disbonds, cracks, or flaws in the coating.
Another object of the present invention is to provide a means and method as above described which is efficient, economical, and reliable.
A further object of the present invention is to provide a means and method as above described which is flexible with regard to its application to a variety of coatings and electrically conducting materials and in its ability to characterize defects in coatings.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.